I've just installed the new CLAM Wallet on MacOSX Yosemite.  I loaded the application and it started to download the blockchain.  I closed the client and then I was able to copy across the blockchain and wallet from my Windows machine.  Files were copied from Windows (%appdata%\Clam) to MacOSX (~/Library/Application Support/Clam).  I restarted the client after the copy was complete and the blockchain and wallet were available and in sync.

The only thing I had to change in the new client was to stop using the black visual theme (under Options => Display) so that I could see the mouseover text for the locked/encrypted, staking, network connections, up to date icons (in the bottom left of the window).  When using the black visual theme, the transparency was hard to read.  I tried it against my dark wallpaper/background and against a light background but it didn't really make a difference.  I do like the black theme but I can't use it atm.